Unstoppable delta variant and waning Covid-19 vaccine effectiveness
The high number of cases and deaths are not just occurring in low-vaccinated countries but even in high-vaccinated nations such as UK, US, Japan and Brazil.

ByDebananda S Ningthoujam

Updated on 21 Aug 2021, 4:54 pm

(File Photo: IFP)

(File Photo: IFP)

The delta variant is still surging unstoppably around the world. According to the latest data given by Johns Hopkins University Coronavirus Resource Center (Aug. 21, 2021), about a dozen countries have reported new daily cases in the range of approximately 20,000-30,000 including India. These nations include Brazil (33,887 cases, 870 deaths), France (23,482 cases, 96 deaths), India (34,457 cases, 375 deaths), Indonesia (20,004 cases, 1,348 deaths), Iran (28,833 cases, 555 deaths), Japan (25,892 cases, 39 deaths), Malaysia (23,564 cases, 233 deaths), Mexico (21,734 cases, 775 deaths), Philippines (16,797 cases, 317 deaths) and the United Kingdom (37,128 cases, 114 deaths). The US currently seems to be an outlier with the latest figures of 319,456 cases and 2,677 deaths (however, this data needs to be verified from other sources). Among the worst-affected countries (excluding the US), Japan reported the least number of deaths (39) and Brazil the highest (870 deaths).

The vaccine-induced immune response wanes significantly after 90 days

The high number of cases and deaths are not just occurring in low-vaccinated countries but even in high-vaccinated nations such as UK, US, Japan and Brazil. The current surge in infections is driven by the highly infectious delta strain of SARS-2 coronavirus. There are now reports that a single dose of most vaccines including CoviShield doesn't confer adequate protection against this variant. There are now reports that even in fully vaccinated (those who have received 2 doses), the vaccine-induced immune response wanes significantly after 90 days (after getting the 2nd shot).

We must seriously note that a single dose of a vaccine doesn't give significant protection against the delta variant! This means that the majority of our eligible population (70-80%, at least) must be fully vaccinated (administer 2 shots) at the fastest possible time to prepare for a possible third wave. In addition, we must make plans to administer the booster shot (third dose) as soon as possible. And, we need to vaccinate our children (people below 18) as soon a pediatric vaccine becomes available. I shall address these issues later in this column.

First, the need for the 2nd dose to protect ourselves against the delta strain. Indian Express (Aug. 18, 2021) has reported the findings of a study led by Dr Ruma Satwik, Ganga Ram Hospital, Delhi involving 4,276 healthcare workers. Of these employees, 2,716 had received 2 doses of CoviShield, 623 got a single dose, and 927 were unvaccinated. The study was conducted during March 1-May 31, 2021 when the delta strain started surging. It was found that 12.3% of singly jabbed individuals contracted symptomatic infections while the rate was 13.9% among the unvaccinated. That is, a single shot provided only marginal protection against symptomatic infections. The protection was increased to 28% after 2 doses (given at a median interval of 30 days).

Fully vaccinated people (those who got 2 doses) had 67% protection against moderate to severe disease, 76% against supplemental oxygen therapy, and about 97% against deaths. The corresponding figures for singly-jabbed people were much lower. This study has now been published in the European Journal of Internal Medicine.

Those who received 2 doses after a previous COVID infection has much higher protection against all major outcomes

Another interesting finding of this study is that those who received 2 doses after a previous COVID infection has much higher protection against all major outcomes: 93% against symptomatic infections, 98% to mild and moderate disease, and 85% against oxygen therapy. These findings emphasize the need to fully vaccinate (administer 2 doses) the majority of the population as promptly as possible. We may prioritize fully vaccinating those who were never infected before.

Second, the immunity triggered by 2 doses of AstraZeneca or Pfizer vaccine against the delta variant wanes significantly in 90 days (3 months). An Oxford University-led study (India Today, Aug. 19, 2021) reports that efficacy of protection against symptomatic infections was initially 85% for Pfizer and 68% for AstraZeneca vaccines (2 weeks after the 2nd dose). However, this got reduced to 75% and 61% respectively, 90 days after receiving the 2nd shot. That's why several nations especially Israel, UK and US are now administering or considering giving booster doses to their citizens to provide adequate protection against delta strain.

US authorities have now outlined a plan for administering a third shot

After much controversy about the need for a booster dose, the US authorities have now outlined a plan for administering a third shot, after receiving the 2nd dose of Pfizer or Moderna vaccine (TOI, Aug. 18, 2021). The booster shots in the US are scheduled to begin from September 20, 2021. Israel has already began giving booster doses to its citizens from Aug. 1, 2021 for those aged over 60, which was later extended to people of over 50 years. Most recently, the country has extended the booster shots to citizens above the age of 40.

Dr Priya Abraham, Director, National Institute of Virology (NIV), Pune, has recently said that the booster dose will be recommended in India in the near future (HT, Aug. 19, 2021). Dr Cyrus Poonawalla, CEO, SII (maker of CoviShield), has also revealed that he has taken the booster dose as also 7,000-8,000 employees of Serum Institute of India (SII). He said "After six months, the antibodies go down and that is why I have taken the third is my request to take a booster dose (third dose) after six months."

World's first DNA vaccine against COVID-19

Indian authorities have granted emergency use approval (EUA) to the world's first DNA vaccine against COVID-19, manufactured by Zydus Cadila (BBC News, Aug. 21, 2021). This is the second indigenous vaccine after Covaxin made by Bharat Biotech. It's a 3-dose vaccine to be given on day 0, day 28, and day 56. It has about 66% effectiveness against symptomatic infections. The trial for the vaccine involved 28,000 volunteers in over 50 centres, which included 1,000 children in the 12-18 age group. This is the first India-made vaccine that can be given to people of age 12 and above, that's it can be administered to adults as well as the teens.

Vaccine Suitability for Children 

There are many plus points for this vaccine. First, it is quite suitable for children as the injection may be given intradermally pain-free by an applicator, without using a needle. The vaccine can be best stored at 2-80 C, however, it remains stable at 250 C for 3 months. That means it may be transported more easily as the sophisticated cold chain storage needs are avoided. The vaccine uses 'plasmids', small rings of DNA, that contain the genetic information for the spike protein of SARS-2. Once inside the body, the vaccine stimulates the body to make a fragment of the spike protein which stimulates the body's immune system to produce antibodies and activated immune cells that help the body fight the virus efficiently. The price of the vaccine is yet to be announced.

Another vaccine of Novavax company which will be quite novel as it's a nasal vaccine, is likely to be launched by October-November 2021. The vaccine uses protein subunit as the core component and is on a very different platform compared to AstraZeneca, Pfizer, Moderna or Johnson and Johnson vaccines.

Coronavirus vaccines for children may become available in September-October 2021

As discussed above, the Zydus Cadila vaccine may be administered to children in India possibly sometime in September 2021. That will go a long way in assuaging the concerns of parents of school-going children.

Another pediatric vaccine undergoing train in India is Covaxin made by BB. The trail involves 525 children above the age of 2.  The trial is going on at AIIMS, Delhi and 5 other hospitals. This vaccine may become available in September-October 2021, after final analysis of trial data (NEWS 18, Aug. 19, 2021).


First published:21 Aug 2021, 4:54 pm


Debananda S Ningthoujam

Debananda S Ningthoujam

The author teaches and studies microbial biochemistry and biotechnology at Manipur University

Top Stories

Loading data...


Loading data...


Have a complaint, a suggestion or just some feedback about our content? Please write to and we’ll do our best to address it.